PNW 548 June 2001

Fall and Winter Vegetable Gardening in the Pacific Northwest

Oregon State University +

University of Idaho L

Washington State University Fall and Winter Gardening in the Pacific Northwest

P. Patterson ith a little extra planning and care, you can enjoy fresh vegetables from your garden most of the year. Many cool-season crops produce well in the fall and, in mild-winter W areas of the Pacific Northwest, hold through the winter if protected. You can plant these vegetables in mid- to late summer after you harvest spring crops and as space is available. To be successful, you need to plan ahead, choose varieties wisely, and give proper care to your plants. Keep in mind that fall and winter weather can vary greatly from year to year. A crop that fails one year due to an unusually early freeze or an abnormally cold winter might thrive in a milder year. Be willing to experiment, and don’t give up if your results some years are less than ideal. GETTING STARTED Choosing varieties all gardening is possible in most parts of the Pacific Northwest. Late plantings of warm- Fseason crops such as corn and beans can be harvested until the first killing frost. Cool-season crops, such as kale, turnips, mustard, broccoli, and cabbage, withstand frost and grow well during cool fall days. In fact, some of the best vegetables are produced during the warm days and cool nights of fall. These environmental conditions add sugar to sweet corn and crispness to carrots. Parsnips, kale, collards, Brussels sprouts, and Jerusalem artichokes are examples of crops that are improved by a touch of frost. Winter gardening is possible in mild-winter areas west of the Cascades. With a little protection, cool-weather crops can be harvested throughout the winter. In addition, some fall- planted crops (for example, certain varieties of broccoli, carrots, and onions) will grow slowly through the winter and be ready to harvest early in the spring. Choose varieties that are suited to fall and winter harvest. Some varieties are designated specifically for fall planting, while others perform well only in the spring. Table 1 lists some good varietal selections for several vegetables that are appropriate for fall and winter gardens. Consult seed catalogs for additional information.

Pat Patterson, Extension program assistant (home horticulture), Lane County, Oregon State University 2 Table 1.—Vegetables for fall and winter gardening Minimum Start well Store Early spring Recommended Crop temperature (°F) ahead in garden* harvest varieties/Comments Beet 15 •• •Winterkeeper, Albina Verduna. Will resprout in spring for greens. Broccoli 10 • Purple Sprouting, White Sprouting Late, Rudolph Brussels sprouts 10 • Jade Cross “E”, Lunet, Oliver, Red Rubine Cabbage 10 •• •Danish Ballhead, Excel, Gloria, Melissa, Zerlina Carrot 15 • Bolero, Merida, Royal Chantenay Cauliflower 10 • Snow Crown, Snow Ball Celeriac 20 Can go to 10°F if cloched. Celery 10 ••Utah Improved. Needs some protection. Celtuce 20 Can go to 10°F if cloched. Chives 0 • Collard 0 • Champion Corn salad, 0 • Use small-leaf varieties. fetticus, feldsalat, lambs’ lettuce Cress, winter 15 Endive 10 President, Perfect. Best under cloche. Fava bean 15 Aquadulce, Sweet Lorane for eating. Plant September– August for May harvest. Many varieties are even hardier. Fennel 20 Can go to 10°F if cloched. Self-sows freely. Garlic 0 • Mulch. Horseradish 0 • Restrict spread! Jerusalem artichoke 0 •• Restrict spread! Kale 0 • Winter Red, Winterbor, Siberian Kohlrabi 15 • Grand Duke, Kongo, Winner Leek 0 •• Durabel, Alaska, Goliath, Siberia, Mekwina Lettuce, leaf 15 • Winter Density, Oak Leaf, Top Gun, Merveille des Quatre Saisons (also known as Continuity). Best under cloche to prevent rain damage. Mustard 20 • Mizuna. Can go to 10°F if cloched. Onion 0 • Bulbs: Walla Walla, Keepwell, Hi-Ball, Buffalo, Red Cross. Bulblets and tops: Egyptian Top, Multiplier. Scallions: Hardy white bunching (Scallions usually are better in spring.) Parsley 0 • Italian plain leaf; curled types with some protection. Parsnip 0 •• Cobham Marrow, Gladiator Radish, Oriental 10 ••All Season’s White Long, China Rose Rutabaga 20 • Marian, American Purple Top, Improved Laurentian. Can go to 10°F if cloched. Salsify 0 •• Spinach 0 • Bloomsdale Savoy, Tyee, Skookum, Olympia, Hybrid 424, Melody, Wolter Baker, St. Helens. Plant in well-drained soil. Swiss chard 10 • Perpetual, Dorat, Ruby Red. Even spring-planted chard often comes through the winter and resprouts. Turnip 10 • Purple Top White Globe. Also good for late fall harvest. *Mature vegetables can be stored in the ground and used as needed. 3 Choosing a location he first key to a successful fall or winter garden is location. Much depends on your garden’s Tmicroclimate. Microclimates vary from yard to yard (for example, urban gardens tend to be warmer than rural gardens) and within a single yard. Choose the warmest location you have. Don’t plant in a spot that is prone to early frost (for example, at the bottom of a hill) or exposed to the wind. Look for an area that gets as much sun as possible during the short days of autumn and winter, such as a south-facing slope. If possible, place your garden where it is easily accessible. It’s no fun to slog through winter’s mud and cold rain to harvest your crops. To reduce insect and disease problems, don’t plant crops where a related vegetable was growing. For example, put broccoli in a spot vacated by peas, not by cabbage. See OSU Extension publication FS 242, Preventing Plant Disease in Your Garden and Landscape (“For more information,” page 8). Preparing the soil or crops that will be in the garden during the rainy season, good drainage is essential. Raised Fbeds are best. If your soil doesn’t drain well, amend it with organic matter such as compost. Prepare the soil by restoring nutrients removed by spring and summer crops. A light layer of compost or aged manure, or a small application of a complete chemical or organic fertilizer, boosts soil nutrients in preparation for another crop. PLANTING AND EARLY CARE When to plant for fall harvest imely planting is another key to a successful fall garden. The crops need time to mature Tbefore cold weather and short days curtail growth; but, if you plant too early, the young plants might wilt in the heat or mature too soon. To determine the time to plant a particular vegetable for the latest harvest, you need to know the average date of the first killing frost in your area and the number of days to maturity for the variety grown. Choose the fastest maturing varieties for late plantings. The formula below can help you determine when to start your fall garden. Number of days from seeding or transplanting outdoors to harvest + Number of days from seed to transplant (if you grow your own transplants) + Average harvest period + Fall factor (about 2 weeks) + Frost-tender factor (if applicable) = Days to count back from first frost date The fall factor takes into account the fact that plants grow more slowly during the cool, short days of autumn. The frost-tender factor is added only for those crops that are sensitive to frost (e.g., corn, beans, cucumbers, tomatoes, and squash). These crops must mature 2 weeks before frost to produce a reasonable harvest. Presprouting seeds ou can reduce the fall factor by 2 to 5 days by presprouting seeds indoors. Almost any crop Ycan benefit from presprouting. To presprout seeds, place them between two layers of damp paper towels. Place the towels in a plastic bag and keep them in a warm place until the seeds germinate. Another method is to soak seeds for 4 hours. Allow the seedlings to reach a length of up to 1 inch. Be careful not to break the roots when planting. You can plant sprouted seeds more deeply than normal to help prevent drying out. Water well until the plants break the soil surface.

4 When to plant for winter harvest rops that go through the winter in mild areas of the Pacific Northwest must be well Cestablished, but not mature, unless you simply are storing them in the ground (i.e., root vegetables such as carrots and leeks). Most winter crops are planted from June to early August. Table 2 shows recommended planting dates for several winter vegetables. Table 2.—Recommended planting dates for winter vegetables.*

Crop Planting date Planting method Beet July 15 Seed Broccoli June Transplant or seed July Brussels sprouts July 10–15 Transplant Cabbage, extra early June Transplant or seed July 15–August 1 Cabbage, late May 20–June 25 Transplant or seed Carrot July 15 Seed Celeriac June Transplant Celery June 1–July 15 Transplant Chinese cabbage July 1–15 Seed Collard July 15 Seed Corn salad September Seed Fava bean September; February 1–March 31 Seed Kale June Transplant or seed July 20–August 10 Kohlrabi June Transplant or seed July 20–August 10 Lettuce, head To July 15 Transplant or seed Lettuce, leaf To August 10 and Transplant or seed December–January Mustard August 15–October 10 Seed Onion, bulbing August 1 Sets Onion, multiplier September Sets Parsnip May 15–June 15 Seed Rutabaga July 10–31 Seed Spinach August 1–15 Transplant or seed Swiss chard June–July Seed Turnip August Seed *Dates recommended are for the mid-Willamette Valley, Oregon. Planting dates might vary in other areas. Early care f it’s hot and sunny when you plant, your young plants will need extra care. Water transplants Idaily at first. You might need to sprinkle seeds and newly germinated seedlings twice a day. To keep the soil moist and protect young plants from the sun, temporarily shade them. Boards and umbrellas make good shade structures. Once young plants are established, you can use a mulch to hold moisture in the soil and control weeds. Irrigate when necessary, so the young plants have sufficient moisture.

5 Fall plantings tend to have few insect problems, as they avoid the peak insect activity of midsummer. However, some insects, such as cabbage worms and cabbage root maggots, may be worse late in the year. Row covers and cloches help deter insects as well as extend the season (see “Season extenders”). Vegetables that remain in the ground throughout the winter need some extra care. The following suggestions can make your winter garden more successful. • Remember to control snails and slugs in August and September, especially if you mulch your plants. By reducing the population in early fall before the breeding season, you’ll have less trouble during the winter (and next spring as well). • Do not fertilize overwintered crops late in the fall. Too much nitrogen encourages a flush of new growth, which is susceptible to freezing.

Figure 1.—Cold frame. • When thinning, leave extra space between plants that will stay in the garden over the winter. Closely spaced plants are more susceptible to rots and slug damage in cool, wet weather than are those with adequate air circulation. PREPARING FOR FROST all garden care intensifies when the weather forecast predicts the arrival of frost. Your main Fconcern then should be to harvest all ripe, tender crops before they are chill damaged. For example, tomatoes, summer squash, melons, eggplants, cucumbers, and peppers cannot withstand frost and should be picked immediately. Store the vegetables until needed. If the frost warning is mild (the temperature is not expected to fall below 30°F), try covering tender plants that still hold a lot of immature fruit. Baskets, burlap or canvas sacks, boxes, blankets, or buckets help protect plants from frost. Warm days will mature some of the fruit as long as the plants have nightly frost protection. Cool-weather crops such as cabbage, broccoli, kale, carrots, many salad greens, Brussels sprouts, leeks, beets, turnips, scallions, parsley, cilantro, and spinach can withstand some frost. Some of these crops are quite hardy and will survive temperatures well below freezing; others can be damaged by temperatures below 30°F. See “Season extenders” for ways to keep these plants growing well past the first frost.

Figure 2.—Dutch light. SEASON EXTENDERS rotection from incessant rain can extend the life of a winter garden dramatically. Heavy and Pprolonged rains can saturate the soil, encourage slugs, and create an ideal environment for leaf diseases. By covering your winter crops with a cloche, cold frame, row cover, Wall-o-waterTM, plastic mulch, or other product, you can avoid many of these problems and extend the growing season. The following structures protect plants from frost as well as heavy rain. Cold frames and hotbeds old frames and hotbeds are inexpensive structures for growing cool-weather crops. Cold Cframes rely on the sun for their sole source of heat (Figure 1). Heat is collected when the sun’s rays penetrate clear plastic, glass, or fiberglass. Hotbeds are heated by soil-heating cables, steam-carrying pipes, or fresh, strawy manure buried beneath the plant rooting zone. Cold frames he ideal location for a cold frame is on a southern or southeastern slight slope to ensure Tgood drainage and maximum exposure to sun. A sheltered spot with a wall or hedge to the north protects against winter winds. Sinking the frame into the ground a bit also provides earth insulation. Figure 3.—Solar pod. To simplify use of a cold frame, consider a walkway to the front, adequate space behind the frame for removing the top, and perhaps a counterbalance to make it easier to raise and lower the top. Some gardeners make their cold frame lightweight enough to be moved from one section of the garden to another. An example is the Dutch light, which is a large but portable, greenhouse-like structure (Figure 2).

6 Frames can be built from many materials; wood and cinder block are most common. If you use wood, choose a species that resists decay or one of the new plastic materials that look like wood. Never use creosote- or pentachlorophenol-treated wood, because these substances can vaporize easily and are harmful to plants and humans. Frame kits are available, some of which contain automatic ventilation equipment. There is no standard size for a cold frame. Size depends on the amount of available space and desired crops. Do not make the frame so wide that you can’t reach all parts of the interior for weeding and plant care; 4 to 5 feet usually is the maximum width. A simple method of insulation is to place burlap sacks filled with leaves over the frame at night to protect against freezing. Another method is to stack bales of straw against the frame. New cold frame designs include systems for passive solar energy storage, such as black containers filled with water that absorb heat during the day and release it at night. An example is the solar pod, which is shaped like a tunnel (Figure 3). Other designs have a very high back and a steeply sloped glass top. Some designs include movable insulation that is folded up during Figure 4.—Plastic jug cloche. the day and unfolded at night or during extremely cold weather. Ventilation is most critical in late winter, early spring, and early fall on clear, sunny days when temperatures rise above 45°F. Raise the top to prevent heat buildup inside the frame. Lower it early enough to conserve heat for the night. An automatic, nonelectric lifter is a good investment. Hotbeds A cold frame can be converted to a hotbed. For a manure-heated bed: 1. Dig out an area 8 or 9 inches deep (deeper if you need to add gravel for increased drainage). 2. Add an 8-inch layer of strawy horse manure. 3. Cover with 6 inches of good soil. For an electric-heated bed: 1. Dig out an area 8 or 9 inches deep. 2. Lay down thermostatically controlled electric cable in 6- to 8-inch loops, evenly spacing the cable but never allowing it to cross. 3. Cover with 2 inches of sand or soil. Figure 5.—Fiberglass tunnel 4. Lay out hardware cloth to protect the cable. cloche. 5. Cover with 4 to 6 inches of good soil. Cloches and row covers loches originally were bell-shaped glass jars set over delicate plants to protect them from the Celements. The definition now includes many types of portable structures that shelter plants from drying winds, rain, and cold air. Cloches are set over individual plants or made into tunnels for whole rows. They trap solar radiation and moisture evaporating from the soil and plants. Cloches generally are lightweight, portable, and reusable. The best designs can be closed completely at night to prevent frost damage and opened or removed completely during the day for good air circulation. Make sure cloches are anchored or are heavy enough so they don’t blow away. The hotcap and the cut-off plastic jug are simple cloches (Figure 4). More elaborate ones include fiberglass tunnels (Figure 5), special plastic cloches, row covers with slits to allow aeration, and panes of glass connected by specially designed hinges to form a tent (Figure 6). You can assemble an excellent Quonset-type cloche quickly by covering a 5- to 6-foot piece of concrete reinforcing wire with row cover or plastic. The heavy-duty wire comes in 5- and 7-foot lengths. It is strong enough to shrug off snow loads. Figure 6.—Glass tent cloche.

Figures 4–6 reprinted by permission from Short-Season Vegetable Gardening, PNW 497, University of Idaho. 7 FOR MORE INFORMATION OSU Extension publications • Constructing Cold Frames and Hotbeds, FS 246 (published 1980, reprinted 1996). No charge • Eastern Oregon Vegetable Garden Guide, EC 1491 (published 1997, reprinted 1998). $1.50 • Gardening with Composts, Cloches, and Row Covers, EC 1247 (published 1986, reprinted 1999). $1.00 • Preventing Plant Disease in Your Garden and Landscape, FS 242 (revised 2000, reprinted 2000). No charge • Short Season Vegetable Gardening, PNW 497 (published 1997, reprinted 2000). $2.00 • Slugs, FS 277 (Revised 1993, reprinted 2000). No charge Portions of this publication originally were published as part of Sustainable Gardening: The Oregon-Washington Master Gardener Handbook, EM 8742 (Oregon State University, Corvallis, published 2000). To order copies of the above publications, send the complete title and series number, along with a check or money order for the amount listed, to: Publication Orders Extension and Station Communications Oregon State University 422 Kerr Administration Corvallis, OR 97331-2119 fax: 541-737-0817 If you would like additional copies of this publication, Fall and Winter Gardening in the Pacific Northwest (PNW 548), send $1.50 per copy to the above address. You may order up to six no-charge publications without charge. If you request seven or more no-charge publications, include 25 cents for each publication beyond six. We offer discounts on orders of 100 or more copies of a single title. Please call 541-737-2513 for price quotes. Other publications • Solomon, S. Growing Vegetables West of the Cascades, Sasquatsch Publishing, Seattle, 1989. World Wide Web You can access Pacific Northwest Extension publications through the Web at: eesc.orst.edu (Oregon State University) info.ag.uidaho.edu (University of Idaho) pubs.wsu.edu (Washington State University)

© 2001 Oregon State University

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the Oregon State University Extension Service, Washington State University Cooperative Extension, the University of Idaho Cooperative Extension System, and the U.S. Department of Agriculture cooperating. The three participating Extension Services offer educational programs, activities, and materials—without regard to race, color, religion, sex, sexual orientation, national origin, age, marital status, disability, and disabled veteran or Vietnam-era veteran status—as required by Title VI of the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and Section 504 of the Rehabilitation Act of 1973. The Oregon State University Extension Service, Washington State University Cooperative Extension, and the University of Idaho Cooperative Extension System are Equal Opportunity Employers.

Published June 2001. $1.50